The present invention relates to a ratchet wrench, and more particularly to such a ratchet wrench in which the angle of action produced between the stop member and the ratchet wheel is minimized, so that maximum torsional force can be achieved.
A variety of ratchet wrenches have been disclosed, and have appeared on the market. FIGS. 1 and 2 show two different structures of ratchet wrench according to the prior art, in which a stop member is forced into engagement with the ratchet wheel to control the direction of rotation of the ratchet in the box in one end of the wrench body. Because a great contained angle is defined between the ratchet wheel and the stop member, much ineffective component of force is produced during the operation of the ratchet wrench. Further, the cover plate, which holds the ratchet wheel in the box, tends to be damaged or permanently deformed during the operation of the ratchet wrench because it is fastened to the wrench body by screws. FIGS. 3 and 4 show another structure of ratchet wrench according to the prior art. According to this design, the stop member receives a driving force from the ratchet wheel at 90xc2x0 and 180xc2x0 respectively, and a great contained angle is defined between the stop member and the tangent line. During the operation of the ratchet wheel, a great ineffective component of force is produced. Further the limited area of bearing force causes the stop member unable to bear a high torsional force. FIGS. 5 and 6 show still another two structures of ratchet wrench according to the prior art. Due to the limitation of the angular position of the stop member, a great ineffective component of force is produced during the operation of these ratchet wheels. In FIG. 5, a steel ball is provided to stop the ratchet wheel. This design can not bear much torsional force. In FIG. 6, a great ineffective component of force is produced during the operation of the ratchet wrench, causing the ratchet wheel to be deformed easily. FIG. 7 shows still another structure of ratchet wrench according to the prior art. According to this design, the stop member is disposed in a horizontal position, which bears less torsional force, and tends to produce a great reactive force to the ratchet wheel, causing the ratchet wheel to be deformed permanently. The drawbacks of the aforesaid prior art ratchet wheels are produced due to improper angular position design of the stop member relative to the ratchet wheel.
The present invention has been accomplished to provide a ratchet wheel, which eliminates the aforesaid drawbacks. According to the present invention, the side hole in which the stop member is installed and forced by a spring member into engagement with the ratchet wheel in the box in one end of the wrench body defines with the horizontal line which passes through the center of the box a contained angle at about 8xcx9c18xc2x0. This design greatly reduces the angle of action between the stop member and the ratchet wheel during the operation of the ratchet wrench, so that the inactive component of force can be minimized.